Oxytocin's Fingerprint in Personality Traits and Regional Brain Volume

Abstract

Oxytocin has a fundamental role in social behavior. In humans, supporting evidence shows that oxytocin enhances people's ability to trust or affiliate with others. A key question is whether differences in plasma oxytocin concentration in humans are related to people's differences in their social traits of personality and if such differences are reflected in the structural organization of brain areas responsive to the action of this hormone. We examined the correlation between oxytocin plasma levels and personality traits in 30 healthy subjects, tested with the Inventory revised neuroticism-extroversion-openness personality inventory (NEO-PI-R). By using the voxel-based morphometry technique, we also investigated changes in gray matter volume as a function of the plasma oxytocin level and NEO-PI-R scores. A positive correlation was found between plasma oxytocin and extraversion scores, a dimension that captures social affiliative tendencies. Moreover, we found an inverse correlation between plasma oxytocin and the volume of the right amygdala and the right hippocampus, 2 brain areas implicated in fear and anxiety. Finally, we showed that the amygdala-hippocampal complex correlate negatively with extraversion scores. Our findings provide evidence for a neural mechanism linking physiological oxytocin's variability and structural variation of brain regions relevant for emotion regulation to individual differences in affiliative personality traits.

Sex, Receptors, and Attachment: A Review of Individual Factors Influencing Response to Oxytocin

“…Some of these changes, notably, are mediated via epigenetic modulation of the OT system (Cushing and Kramer, 2005; Stolzenberg et al, 2012). More recently, human experiments support the hypothesis that dynamic changes in components of the OT system (i.e., methylation of the OTR gene; Jack et al, 2012; Unternaehrer et al, 2012) and possibly neurodevelopmental changes in OT sensitive brain structures (see Andari et al, 2012 for discussion) are some of the proximate effectors through which early parental care impacts an individual throughout life (Champagne et al, 2001; Champagne, 2008; Gordon et al, 2011; Bales and Perkeybile, 2012 for reviews). Other convergent evidence comes from attachment-informed behavioral research which indicates parallels and reciprocal influence between parental and infant OT levels and the species-specific behaviors associated with secure attachment and optimal psychosocial development (Feldman, 2012).…”

“…Though the focus here is only on variation in the OTR and CD38 gene, other potential contributors to neuropeptidergic individuality include: (1) differences in baseline and dynamic levels of OT release in the brain and/or secretion into the plasma, the latter found to correlate with personality and brain structure (Andari et al, 2012); as well as (2) differences in regional OTR and AVPR receptor density, a factor which influences the social behavior of rodents (Hammock and Young, 2006; Ross et al, 2009; Ophir et al, 2012). Though a few studies have examined postmortem OTR density in the human CNS (Loup et al, 1989, 1991), as mentioned in the accompanying review (MacDonald and Feifel), synthesis of a small-molecule radioligand for the OTR (Smith et al, 2012a), would greatly facilitate our understanding of the role of OTR density and location in living humans.…”

Personality is tightly coupled to vasopressin-oxytocin neuron activity in a gregarious finch

“…Findings in humans likewise suggest that OT modulation varies in relation to sex, context, and personality. For instance, plasma OT levels correlate positively with Extraversion scores (Andari et al, 2012), and OT nasal spray produces neural and behavioral responses in the Prisoner's Dilemma game that are strongly sexually differentiated (Rilling et al, 2013). A variety of other data further suggest that OT effects on human behavior are dependent upon situational variables (context) as well as individual personality (Bartz et al, 2011).…”

A Precision Medicine Approach to Oxytocin Trials

“…Genomic analysis and evaluation of postmortem brain samples are possible. Some researchers measure baseline concentrations of oxytocin (plasma or saliva or urinary) to compare OT levels between individuals with a high degree of sociability and introverted individuals, or between healthy subjects and others with psychiatric disorders (Andari et al 2010, 2014; Jacobson et al 2014; Jansen et al 2006). This can also serve to correlate baseline OT concentrations with other social behaviors such as parent–infant synchrony (Feldman et al 2007).…”

“…Also, more research is needed to better understand the degree of correlation between peripheral measurements and central actions of OT. However, despite these above challenges, there is an increasing body of evidence showing that OT can be used as a biomarker of social functioning (Andari et al 2014; Parker et al 2014). Genetic variants or plasma oxytocin are associated with the variance in social cognition.…”